Microservices # restTemplate.postForObject

 

Java 8 POST request example that sends a JSON payload to a REST API. I’ll show you both the plain Java HttpURLConnection way and the Spring Boot RestTemplate way, since you often work with microservices.

🟢 Option 1: Pure Java 8 (HttpURLConnection)

import java.io.OutputStream;

import java.net.HttpURLConnection;

import java.net.URL;

 

public class PostRequestExample {

    public static void main(String[] args) {

        try {

            // API endpoint

            URL url = new URL("https://jsonplaceholder.typicode.com/posts");

            HttpURLConnection conn = (HttpURLConnection) url.openConnection();

 

// Set request method and headers

conn.setRequestMethod("POST");

conn.setRequestProperty("Content-Type", "application/json; utf-8");

conn.setRequestProperty("Accept", "application/json");

conn.setDoOutput(true);

 

// JSON payload

String jsonInputString = "{ \"title\": \"Java POST\", \"body\": \"Hello from Java\", \"userId\": 1 }";

 

            // Write JSON to request body

            try (OutputStream os = conn.getOutputStream()) {

                byte[] input = jsonInputString.getBytes("utf-8");

                os.write(input, 0, input.length);

            }

 

            // Read response

            try (java.io.BufferedReader br = new java.io.BufferedReader(

                    new java.io.InputStreamReader(conn.getInputStream(), "utf-8"))) {

                StringBuilder response = new StringBuilder();

                String responseLine;

                while ((responseLine = br.readLine()) != null) {

                    response.append(responseLine.trim());

                }

                System.out.println("Response: " + response.toString());

            }

 

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

}

🟢 Option 2: Spring Boot (RestTemplate)

import org.springframework.http.HttpEntity;

import org.springframework.http.HttpHeaders;

import org.springframework.http.MediaType;

import org.springframework.web.client.RestTemplate;

 

public class PostRequestSpringExample {

    public static void main(String[] args) {

        RestTemplate restTemplate = new RestTemplate();

 

        String url = "https://jsonplaceholder.typicode.com/posts";

 

        // JSON payload

        String jsonPayload = "{ \"title\": \"Spring POST\", \"body\": \"Hello from Spring Boot\", \"userId\": 2 }";

 

        // Set headers

        HttpHeaders headers = new HttpHeaders();

        headers.setContentType(MediaType.APPLICATION_JSON);

 

        // Wrap payload + headers

        HttpEntity<String> request = new HttpEntity<>(jsonPayload, headers);

 

        // Send POST request

        String response = restTemplate.postForObject(url, request, String.class);

 

        System.out.println("Response: " + response);

    }

}

🔑 Key Points

• conn.setDoOutput(true) → enables sending a request body in HttpURLConnection.
• Always set Content-Type: application/json.
• In Spring Boot, RestTemplate.postForObject() makes it much simpler.
• For real-world microservices, you’d typically send a Java object instead of raw JSON, and let Spring handle serialization.